Typically, a hard disk drive is produced, by assembling a magnetic disk or platter revolved by a spindle motor, and a swing arm coupled to an actuator and having a magnetic head into a single assembly. Then, the magnetic disk is formatted by writing servo data containing sector numbers onto it. However, the recent increase in the storage capacity in magnetic disks has caused a significant increase in the time required for writing the servo data. In order to address this time increase, alternative techniques are recently used for writing servo data onto each magnetic disk by a single-disk STW (Servo Track Writer) or for magnetically duplicating servo data onto each magnetic disk by placing a patterned magnetic master in contact with each magnetic disk, before a plurality of such magnetic disks with the servo data written on them are assembled into the single assembly.
These techniques may involve small first-order disk run-out or misalignment of a center axis of the magnetic disk relative to a revolution axis for it, a difference in run-out of a spindle, and shape distortions related to a patterned magnetic master work inaccuracy and a duplication process. However, servo control in a hard disk drive can be provided so as to trace tracks in the form of virtually perfect circles without being affected by such shape distortions, by correcting an amount of the first-order run-out by means of feed-forward control a position of the magnetic head of the hard disk drive, because a disk surface on a data recording area of the magnetic disk is flat.
In recent years, an improved recording medium or a DTM (discrete track medium) magnetic disk for a magnetic disk has been developed, such that adjacent recording tracks on the magnetic disk are magnetically separated to thereby suppress mutual magnetic interference (i.e., cross-erase or cross-talk) between the adjacent tracks and suppress broadening of the recording magnetic domain, and such that spaces between the adjacent tracks are narrowed to thereby increase a storage capacity of the magnetic disk. In the DTM magnetic disk, grooves are formed on the magnetic disk between tracks to be traced by a magnetic head, by a physical machining process such as etching.
PCT International Publication WO 01/031650-A1 published on May 3, 2001 describes a method and an apparatus for writing data onto a recording medium, such as an optical disk and a magnetic disk, and reading data from the recording medium. According to this method, when a block of the medium is defective, the data to be written in this block is stored in an auxiliary memory. Subsequently, all the data from the auxiliary memory is copied to a predetermined spare area of the medium. Conversely, when the medium is read, data is first copied from the spare area of the medium to the auxiliary memory. If a block then appears to be defective, the correct information is read from the auxiliary memory. Thus, it is possible to write and read a real-time audio and/or video signal in a reliable manner without the possible presence of any defective blocks affecting the data transfer rate.
Japanese Patent Application Publication JP 2003-85891-A published on Mar. 20, 2003 describes a non-tracking recording/reproducing system. In this system, information is recorded on a track on a removable disk made of synthetic resins as base materials, according to a packet recording scheme. Thus, a packet is used as a unit to form a track. In this removable disk, recording and reproducing are performed according to a non-tracking scheme. Thus, the track pitch is reduced to be 20 μm or smaller, and the track density is increased so that the capacity of the disk is increased.